The objectives of this project are: (1) To culture postimplantation embryos to aid the laboratory assessment of potential teratogens and the understanding of the molecular mechanisms underlying teratogenesis; (2) to utilize in vitro fertilization (or zygotes) coupled with preimplantation embryo culture, transfer of blastocysts to pseudopregnant recipients and evaluation of "pregnancy outcome" to identify critical early development targets of environmental chemicals.